Coated-wire ion-selective electrode for the determination of thallium(III)

Abstract

The construction, performance characteristics and applications of a coated-wire thallium(III) ion-selective electrode, based on the ion pair between TlCl₄- and the 1,2,4,6-tetraphenylpyridinium cation in a poly(vinyl chloride) matrix, are described. The influence of membrane composition, hydrochloric acid concentration and foreign ions was investigated. The electrode shows a near-Nernstian response over the thallium(III) concentration range 10^–5–10^–2M, with good selectivity and precision. Applications to the potentiometric titration of 0.25–5.0 mg of thallium(III) and to the direct potentiometric determination of thallium in sphalerites and zinc concentrates are reported.